The present invention generally relates to a sieve adjust mechanism and more particularly to a rack and pinion sieve adjustment mechanism applicable to agricultural combines.
In an agricultural harvester combine, the grain is harvested, threshed and cleaned. In conventional agricultural combines, the stocks of grain flow on a conveyer from the harvester to a threshing drum where the grain is loosened from the stock. The grain is then cleaned by passing it through a cleaning assembly.
In most combines, the cleaning assembly contains three main components: a blower, an upper sieve and a lower sieve. The blower has its own housing, whereas the upper sieve and lower sieve are mounted on a cleaning shoe. The sieve consists of a large number of louvers or slats which, based on the crop conditions, need to be opened or closed to control the separating characteristics. Grain is cleaned and separated by passing the grain through the sieves of the cleaning assembly.
FIG. 1 illustrates a conventional sieve adjustment mechanism 100 used in the industry consisting of pivoting handles or lever arms 102 which push or pull the louvers or slats through arm 104 to adjust the size of the sieve opening. However, a problem associated with conventional sieve adjustment mechanisms is that there is generally a significant amount of lost motion or play in the pivot joints of handle 102 and arm 104. The lost motion of conventional sieve adjustments arises from the mechanisms used to adjust the positioning of sieve slats or louvers. Such conventional sieve adjustment mechanisms rely on linkages rotating about fixed pivot points, e.g., 106, as a result there is not a true translation in a single direction of motion so the slats or louvers open or close at different rates during a range of motion of the handles 102. As a result, when a sieve is remotely adjusted using e.g., in-cab electronics, this lost motion/play cannot be easily accounted for and results in less than optimal slat openings or slat openings differing from that set or anticipated by the user.
Thus, there is a need for a system and apparatus for a sieve adjustment mechanism that addresses the aforementioned deficiencies of conventional sieve adjustment mechanisms. Such needs are met by the sieve adjustment mechanism of the present invention.